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ISBN 978-1-932613-67-4
Printed in the United States of America
Third printing June 2014
Edition 9.2
Circular Pipe Head Loss Equation (Head Loss Expressed
in Feet)
4.73 L
h f = 1.852 4.87 Q1.852 , where
C
D
hf
L
D
Q
C
=
=
=
=
=
head loss (ft)
pipe length (ft)
pipe diameter (ft)
flow (cfs)
Hazen-Williams coefficient
Circular Pipe Head Loss Equation (Head Loss Expressed
as Pressure)
U.S. Customary Units
4.52 Q1.85
P = 1.85 4.87 , where
C D
P
Q
D
C
=
=
=
=
pressure loss (psi per foot of pipe)
flow (gpm)
pipe diameter (inches)
Hazen-Williams coefficient
SI Units
P=
6.05 Q1.85
5
# 10 , where
C1.85 D 4.87
P = pressure loss (bars per meter of pipe)
Q = flow (liters/minute)
D = pipe diameter (mm)
Values of Hazen-Williams Coefficient C
Pipe Material
C
Ductile iron
140
Concrete (regardless of age)
130
Cast iron:
New130
5 yr old
120
20 yr old
100
Welded steel, new
120
Wood stave (regardless of age)
120
Vitrified clay
110
Riveted steel, new
110
Brick sewers
100
Asbestos-cement
140
Plastic150
TRANSPORTATION
U.S. Customary Units
a
= deceleration rate (ft/sec2)
A
= absolute value of algebraic difference in grades (%)
e
= superelevation (%)
f
= side friction factor
± G= percent grade divided by 100 (uphill grade "+")
h1
= height of driver's eyes above the roadway surface (ft)
h2
= height of object above the roadway surface (ft)
L
= length of curve (ft)
Ls
= spiral transition length (ft)
R
= radius of curve (ft)
SSD= stopping sight distance (ft)
t
= driver reaction time (sec)
V
= design speed (mph)
v= vehicle approach speed (fps)
W= width of intersection, curb-to-curb (ft)
l= length of vehicle (ft)
y= length of yellow interval to nearest 0.1 sec (sec)
r= length of red clearance interval to nearest 0.1 sec (sec)
Vehicle Signal Change Interval
v
y= t+
2a ! 64.4 G
r = W v+ l
Stopping Sight Distance
SSD = 1.47Vt +
164
V2
a
30 dc 32.2 m ! G n
CIVIL ENGINEERING